Abstract:

Objective    To set up the finite element(FE) model of type II odontoid fracture screw fixation and analyze the stability of fixation on postoperative type II odontoid fracture using different material.   Methods    Atlantoaxial spatial structure information was obtained through CT scanning and 3D finite element model was established. Simulation of stress situation after screw fixation of odontoid fractures was performed; Then comparison of the displacement of the fracture surfaces and stress the fracture surfaces and the screw should take after fixation with screws using two materials(the magnesium alloy and the titanium alloy) were measured; the results were analyzed by t test statistical analysis.　Results　（1）The finite element model of the axis  that consists of 32929 elements and 59265 nodes is of object-like appearance and excellent geometric similarity; ( 2 ) under the circumstance of head extension and flexion, the maximum stress of the titanium alloy screws were 42.3MPa and 62.8 MPa, and the maximum displacement of fracture ends were 0.028mm and 0.040mm respectively; the maximum stress of the magnesium alloy screws was 33.6 MPa and 52.1 MPa and the maximum displacement of fracture ends was 0.036mm and 0.056mm, respectively.　Conclusion　Information of the spatial structure of the axis obtained through CT scanning and utilized for model building can be used in biomechanical experiment; the maximum stress of the screws with two type of materials used for fixation of the pattern-II odontoid fracture is smaller than the yield strength of the material; the stress the fracture ends in the magnesium alloy group was higher than that of the titanium alloy group.

Key words: Odontoid fracture, Magnesium alloy, Hollow screws, Finite element